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Jun 26, 2008

Sonar System For The Blind
Echolocation is a method of perceiving the world by emitting noises, then listening to the reflections of these noises off objects in the environment. Animals use echolocation for hunting and navigation, but visually impaired humans also employ echolocation as part of their orienting repertoire while navigating the world.

Researchers at Boston University have developed a prototype device that can enhance auditory cues while navigating an environment. The device repeatedly emits an inaudible (to humans) ultrasonic click several times per second, and each click reflects off any objects in the environment. The reflections are then detected by special head-mounted microphones, and computer processing converts the ultrasonic signals into audible signals, which the user then can hear over custom open-ear earphones.

The end result is an "auditory image" in which objects in the environment seem to emit "sounds" to the user, with objects of different shapes and textures emitting subtly different sounds, such that the user can distinguish between them. According to BU researcher Cameron Morland, the unique acoustic characteristics of the reflections enable the user to better distinguish the location and size "surface" properties of objects.

The BU team has built a prototype capable of simple detection of objects and open spaces, and preliminary tests show that most people can echolocate a little using the device, and improve quickly with practice. Movies of the device can be found at their web site.

Their paper on this navigation system will be presented at the Acoustics '08 scientific meeting in Paris, France.